Multifocal lens having reduced visual disturbances

ABSTRACT

A method and system provide an ophthalmic device. The ophthalmic device includes an ophthalmic lens having an anterior surface, a posterior surface, at least one diffractive structure and at least one base curvature. The at least one diffractive structure for provides a first spherical aberration for a first focus corresponding to at least a first focal length. The at least one base curvature provides a second spherical aberration for at least a second focus corresponding to at least a second focal length. The first spherical aberration and the second spherical aberration are provided such that the first focus has a first focus spherical aberration and the second focus has a second focus spherical aberration. The first focus spherical aberration is opposite in sign to the second focus spherical aberration.

PRIORITY CLAIM

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 15/051,765 titled “MULTIFOCAL LENS HAVING REDUCEDVISUAL DISTURBANCES,” filed on Feb. 24, 2016, whose inventors areMyoung-Taek Choi, Xin Hong and Yueai Liu, which is hereby incorporatedby reference in its entirety as though fully and completely set forthherein.

BACKGROUND

Intraocular lenses (IOLs) are implanted in patients' eyes either toreplace a patient's lens or, in the case of a phakic IOL, to complementthe patient's lens. For example, the IOL may be implanted in place ofthe patient's lens during cataract surgery. Alternatively, a phakic IOLmay be implanted in a patient's eye to augment the optical power of thepatient's own lens.

Some conventional IOLs are single focal length IOLs, while others aremultifocal IOLs. Single focal length IOLs have a single focal length orsingle power. Objects at the focal length from the eye/IOL are in focus,while objects nearer or further away may be out of focus. Althoughobjects are in perfect focus only at the focal length, objects withinthe depth of field (within a particular distance of the focal length)still acceptably in focus for the patient to consider the objects infocus. Multifocal IOLs, on the other hand, have at least two focallengths. For example, a bifocal IOL has two focal lengths for improvingfocus in two ranges: a far focus corresponding to a larger focal lengthand a near focus corresponding to a smaller focal length. Trifocal IOLshave three focuses: a far focus, a near focus and an intermediate focuscorresponding to a focal length between that of the near and farfocuses. Multifocal IOLs may improve the patient's ability to focus ondistant and nearby objects. Such IOLs may be of particular use forpatients suffering from presbyopia, which adversely affects the eye'sability to focus on both far and near objects.

Although multifocal lenses may be used to address conditions such aspresbyopia, there are drawbacks. A patient may experience increasedincidences of visual disturbances. Visual disturbances are unwanted sideeffects, such as ghost images, halos, glare or hazy vision, due to themultiple focuses of multifocal IOLs. For example, because of thedifferent focal lengths, multiple images may be formed for a singleobject. One image due to the focal length in the appropriate distancerange is in focus, while the ghost image due to the focal length of theother distance range is out of focus. Such ghost images are undesirable.As a result, the intensity and sharpness of ghost images are desired tobe decreased. Similarly, it may be desirable to mitigate other visualdisturbances for multi-focal lenses.

Accordingly, what is needed is a system and method for addressing visualdisturbances in multifocal IOLs.

BRIEF SUMMARY OF THE INVENTION

A method and system provide an ophthalmic device. The ophthalmic deviceincludes an ophthalmic lens having an anterior surface, a posteriorsurface, at least one diffractive structure and at least one basecurvature. The at least one diffractive structure for provides a firstspherical aberration for a first focus corresponding to at least a firstfocal length. The at least one base curvature provides a secondspherical aberration for at least a second focus corresponding to atleast a second focal length. The first spherical aberration and thesecond spherical aberration are provided such that the first focus has afirst focus spherical aberration and the second focus has a second focusspherical aberration. The first focus spherical aberration is oppositein sign to the second focus spherical aberration.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts a plan view of an exemplary embodiment of an ophthalmicdevice.

FIG. 2 depicts a side view of an exemplary embodiment of a lens of anophthalmic device.

FIGS. 3A-3D depict exemplary embodiments of a the intensity versusdistance for lenses made without spherical aberration and with negativespherical aberration in the near focus and positive spherical aberrationin the far focus.

FIG. 4 depicts a side view of another exemplary embodiment of a lens ofan ophthalmic device.

FIG. 5 depicts a side view of another exemplary embodiment of a lens ofan ophthalmic device.

FIG. 6 depicts a side view of another exemplary embodiment of a lens ofan ophthalmic device.

FIG. 7 depicts a side view of another exemplary embodiment of a lens ofan ophthalmic device.

FIG. 8 is flow chart depicting an exemplary embodiment of a method forutilizing an ophthalmic device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary embodiments relate to ophthalmic devices such as IOLs andcontact lenses. The following description is presented to enable one ofordinary skill in the art to make and use the invention and is providedin the context of a patent application and its requirements. Variousmodifications to the exemplary embodiments and the generic principlesand features described herein will be readily apparent. The exemplaryembodiments are mainly described in terms of particular methods andsystems provided in particular implementations. However, the methods andsystems will operate effectively in other implementations. For example,the method and system are described primarily in terms of IOLs. However,the method and system may be used with contact lenses. Phrases such as“exemplary embodiment”, “one embodiment” and “another embodiment” mayrefer to the same or different embodiments as well as to multipleembodiments. The embodiments will be described with respect to systemsand/or devices having certain components. However, the systems and/ordevices may include more or less components than those shown, andvariations in the arrangement and type of the components may be madewithout departing from the scope of the invention. The exemplaryembodiments will also be described in the context of particular methodshaving certain steps. However, the method and system operate effectivelyfor other methods having different and/or additional steps and steps indifferent orders that are not inconsistent with the exemplaryembodiments. Thus, the present invention is not intended to be limitedto the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features described herein.

A method and system provide an ophthalmic device. The ophthalmic deviceincludes an ophthalmic lens having an anterior surface, a posteriorsurface, at least one diffractive structure and at least one basecurvature. The at least one diffractive structure for provides a firstspherical aberration for a first focus corresponding to at least a firstfocal length. The at least one base curvature provides a secondspherical aberration for at least a second focus corresponding to atleast a second focal length. The first spherical aberration and thesecond spherical aberration are provided such that the first focus has afirst focus spherical aberration and the second focus has a second focusspherical aberration. The first focus spherical aberration is oppositein sign to the second focus spherical aberration.

FIGS. 1-2 depict an exemplary embodiment of an ophthalmic device 100that may be used as an IOL. FIG. 1 depicts a plan view of the ophthalmicdevice 100, while FIG. 2 depicts a side view of the ophthalmic lens 110.For clarity, FIGS. 1 and 2 are not to scale. The ophthalmic device 100includes an ophthalmic lens 110 (herein after “lens”) as well as haptics102 and 104. The lens 110 may be made of a variety of optical materialsincluding but not limited to one or more of silicone, a hydrogel, anacrylic and AcrySof®. Haptics 102 and 104 are used to hold theophthalmic device 100 in place in a patient's eye (not explicitlyshown). However, in other embodiments, other mechanism(s) might be usedto retain the ophthalmic device in position in the eye. Thus, thehaptics 102 and/or 104 might be omitted. For clarity, the haptics arenot depicted in FIGS. 2-7, discussed below. Although the lens 110 isdepicted as having a circular cross section in the plan view of FIG. 1,in other embodiments, other shapes may be used. Further, althoughdescribed in the context of an IOL, the ophthalmic lens 110 may be acontact lens. In such a case, the haptics 102 would be omitted and theophthalmic lens sized and otherwise configured to reside on the surfaceof the eye. Thus, the ophthalmic lens 110 may be an IOL or contact lens.

The lens 110 has an anterior surface 112 a posterior surface 114 and anoptic axis 116. The lens is also characterized by a diffractivestructure 120 and a base curvature 130. The lens 110 is a multifocallens having multiple focal lengths. In order to provide multiplefocuses, the anterior and/or posterior surface(s) of the lens 110 mayhave zones corresponding to different ranges in distance perpendicularto the optic axis 116 (i.e. different radii). Stated differently, a zoneis an annular ring along the surface from a minimum radius to a maximumradius from the optic axis 116. For a zonal multifocal refractive lens,each zone may have a different focal length/power. To provide such arefractive lens, the base curvature 130 may be different in differentzones. For a diffractive lens, light traveling through different zonesof the diffractive structure 120 interferes. This zone-to-zoneinterference may result in multiple focal lengths for the lens. Forexample, the diffractive structure 120 may use different diffractiveorders to create multiple focuses. For a bifocal diffractive structure120, the 0^(th) diffraction order may be used for distance focus, and+1^(st) diffraction order used for near focus. Alternatively, a −1^(st)diffraction order may be used for distance focus, and 0^(th) diffractionorder may be used for near focus. For a diffractive lens, the basecurvature 130 is usually considered to have a single zone, or consistentshape, across the surface of the lens 110. In either the refractive ordiffractive case, the lens 110 may be configured to have at least afirst focal length corresponding to a near focus and a second focallength corresponding to a far focus. As their names imply, the nearfocus is closer to the ophthalmic lens 110 in a direction along theoptic axis 116 than the far focus. The near focus thus has a shorterfocal length than the far focus. The lens 110 may thus be a bifocallens. The lens 110 may also have additional focal lengths. For example,the ophthalmic lens 110 may be a trifocal lens including the near focusand far focus described above as well as an intermediate focus betweenthe near and far focuses. In other embodiments, the lens 110 may beconfigured to have another number of focal lengths and focuses.

The lens 110 includes the diffractive structure 120 on the anteriorsurface 112 of the lens 110 and a base curvature 130 on the posteriorsurface 114 of the lens 110. In other embodiments, the diffractivestructure 120 and/or base curvature 130 may reside on different surfaces112 and 114. The combination of the base curvature 130 and diffractivestructure 130 introduce spherical aberrations that are opposite in signinto the far focus and near focus. A positive spherical aberrationresults in the lens refracting central rays (rays closer to the opticaxis 116/center) that are parallel to the optic axis 116 less than ifthe lens was without the spherical aberration. Similarly, a positivespherical aberration results in the lens refracting marginal rays (raysfurther from the optic axis 116/closer to the edges) that are parallelto the optic axis 116 more than if the lens did not have the aberration.A negative spherical aberration results in the lens refracting centralrays that are parallel to the optic axis 116 more than if the lens didnot have the aberration. Similarly, a negative spherical aberrationcauses the lens to refract marginal rays that are parallel to the opticaxis 116 less than if the lens were without the aberration.

The base curvature 130 may introduce a negative spherical aberration forat least one focus, while the diffractive structure 120 may introduce apositive spherical aberration for another focus. The magnitudes andsigns of the spherical aberrations introduced by the base curvature 130and the diffractive structure 120 may not be the same. The basecurvature 130 may introduce negative spherical aberrations into both thenear focus and far focus. The spherical aberrations introduced by thebase curvature 130 usually have the same sign in for all focuses becausethe base curvature is generally a single zone for a diffractivemultifocal lens. The positive spherical aberration may be introducedinto the near focus by the diffractive structure 120. This may beaccomplished by changing the period of step heights of the echeletteswith increasing radial distance from the optic axis 116 from what thelowest order calculations would determine the period should be. It mightalso be possible to introduce a negative spherical aberration in onefocus and a zero spherical aberration in another focus. Thus, the signand/or magnitude of spherical aberrations introduced in differentfocuses by the diffractive structure 120 may be the same or different.

In some embodiments, other changes may be made to the portion of thelens 110 underlying the diffractive structure 120. Such changes will bedescribed herein as changes to the base curvature 130. For example, thebase surface may have multiple zones which have different powers anddifferent spherical aberrations. In such embodiments, the multiple zonebase curvature 130 may provide different spherical aberrations indifferent zones.

Mathematically, the base curvature 130 for a single zone base curvesurface of the posterior surface 114 of the lens 110 may be describedby:z _(base)=[cr ²/(1+sqrt(1−(1+k)c ² r ²)]+A ₄ r ⁴ +A ₆ r ⁶+ . . .  (1)

where z_(base) is the base curvature (the distance the lens surfaceextends in the z direction), r is the distance from the optic axis(radial distance in the x-y plane), c is the curvature, k is a conicconstant and A_(i) are aspheric constants. By utilizing the appropriateaspheric constants in designing the base curvature, the desiredspherical aberration may be introduced. Different amounts of negativespherical aberration may be introduced across the posterior surface 114.Alternatively, the entire posterior surface 114 may have a particularnegative spherical aberration. Thus, the base curvature 130 can beselected to provide the desired level of negative spherical aberrationfor at least the far focus.

In the embodiment shown in FIG. 2, the diffractive structure 120introduces a positive spherical aberration into the near focus. Thus,the spherical aberration introduced by the diffractive structure 120 isopposite in sign to that introduced by the base curvature. The sphericalaberration is introduced only in the near focus because the nature ofdiffraction gratings and diffractive optics allow the diffractivestructure 120 to affect near performance much more strongly than distantperformance.

The diffractive structure 120 is essentially a diffraction grating. Thediffractive structure 120 is shown with respect to a dotted linecorresponding to a lens on which no diffractive structure is provided.The diffractive structure 120 includes echelettes 122. For simplicity,only two echelettes 122 are labeled. However, another number arepresent. The size and spacing of the echelettes may vary across thesurface of the lens 110. For example, the lens 110 may be divided intozones based on the distance from the optic axis (e.g. along the radius).Different zones may have different step heights for the echelettes 122and/or different spacings between the echelettes. Thus, thecharacteristics of the diffractive structure 120 may be controlled byconfiguring the echelettes 122. The profile of the diffractive structure120 is given by:z _(diffractive) =P ₂ r ² +P ₄ r ⁴ +P ₆ r ⁶+ . . .  (2)

where z_(diffractive) is the profile in the z-direction of thediffractive structure 120, r is the distance from the optic axis (radialdistance), P₂ defines the add power and P₄ and P₆ are parameters thatmodify the light distribution. By appropriately configuring the geometryof the echelettes and thus the z_(diffractive), the desired amount ofpositive spherical aberration may be introduced into the near focus. Forexample, changing the spacing between the echelettes 122 further fromthe optic axis (higher radius) may introduce a positive sphericalaberration.

The magnitude of the positive spherical aberration provided by thediffractive structure 120 may exceed a negative spherical aberrationintroduced by the base curvature 120. The net result is that the farfocus and near focus may have different spherical aberrations. Forexample, the far focus may have a negative spherical aberration and thenear focus has a positive spherical aberration introduced by thecombination of the base curvature 130 and the diffractive structure 120.Thus, the lens 110 may have spherical aberration of opposite signs forthe near and far focuses.

The lens 110 may have improved performance while maintaining thebenefits of a multifocal lens. Because the lens 110 is a multifocallens, the ophthalmic device 100 may be used to treat conditions such aspresbyopia. Because the diffractive structure 120 and the base curvature130 provide opposite spherical aberrations in the near and far focuses,the visual disturbances for the lens 110 may be reduced. The effect ofthe introduction of spherical aberrations having opposite signs may beunderstood as follows. Multifocal lenses form multiple images of eachobject. One image is formed for each focus. One of these images will bemore focused than the remaining images. For example, for a bifocal lens,two images are formed: one for the near focus and one for the far focus.For a nearby object, a first image formed due to the near focus is infocus. A second image of the nearby object formed due to the far focushas greater defocus/is less focused. This second image is an unwantedartifact. The combination of the diffractive structure 120 and basecurvature 130 introduce spherical aberrations that have different signsfor different focuses. These spherical aberrations make the image(s)that are less focused less conspicuous. This is accomplished by reducingthe contrast and overall visibility of the image(s) having greaterdefocus. In the example above, the introduction of negative sphericalaberration for the far focus results in the image of the near objectbeing more defocused. The second image described above is moredefocused, less intense and of more uniform intensity. Similarly, theintroduction of positive spherical aberration for the near focus resultsin the near focus providing a larger, lower intensity, more uniformintensity defocused image for far objects. Thus, the introduction ofspherical aberration having opposite signs in the near and far focusesmay reduce image artifacts.

The changes in focus due to the introduction of spherical aberration mayalso be understood graphically. For example, FIGS. 3A and 3B areschematics illustrating the behavior of two lenses. FIG. 3A is a graph140 depicting intensity versus distance without spherical aberrations.The near focus and far focus are also indicated in FIG. 3A. As can beseen in FIG. 3A, the intensity peaks in both near focus and the farfocus. FIG. 3B is a graph 140′ depicting intensity versus distance underthe same conditions but for a lens having a positive sphericalaberration in the near focus and a negative spherical aberration in thefar focus. Thus, the graph 140′ corresponds to a lens analogous to thelens 110 depicted in FIGS. 1-2. As can be seen in FIG. 3B, the energyprofile has been changed from that shown in FIG. 3A. The peaks in thegraph 140′ are spread out and asymmetric because of the added sphericalaberration. As discussed above, a positive spherical aberration in thenear focus results in the corresponding image from a distant objectbeing less focused. Similarly, a negative spherical aberration in thefar focus results in the corresponding image of a near object being lessfocused. As a result, the intensity of a defocused, ghost image may bereduced. Further, the depth of field has been increased. FIGS. 3C and 3Ddepict analogous graphs 142 and 142′ having more realisticcharacteristics. FIGS. 3C and 3D show the cases without sphericalaberration and with positive spherical aberration in the near focus anda negative spherical aberration in the far focus. Thus, the graph 142′thus corresponds to a lens analogous to the lens 110. As can be seen inthe by comparing graphs 142 and 142′, the energy in each peak in thegraph 142′ has been asymmetrically spread out. Consequently, visualdisturbances such a ghost images may be decreased in intensity whileimproving depth of field. As a result, performance of the ophthalmiclens 110 may be improved.

FIG. 4 depicts a side view of another exemplary embodiment of a lens110′ of an ophthalmic device. The lens 110′ is analogous to the lens110. Consequently, the lens 110′ may be used in an ophthalmic devicessuch as the device 100. Further, analogous components have similarlabels. The lens 110′ includes an anterior surface 112′, a posteriorsurface 114′, an optic axis 116, base curvature 130′ and diffractivestructure 120′ having echelettes 122′ that are analogous to the anteriorsurface 112, posterior surface 114, optic axis 116, base curvature 130and diffractive structure 120 having echelettes 122, respectively, ofthe lens 110.

The diffractive structure 120′ resides on the posterior surface 114′,while the base curvature 130′ resides on the anterior surface 112′. Thediffractive structure 120′ and base curvature 130′ introduce sphericalaberrations having opposite signs and, in some embodiments, differentmagnitudes. Thus, the base curvature 130′ may introduce a negativespherical aberration for the at least the far focus. A negativespherical aberration may be provided for the near focus also. Thediffractive structure 120′ introduces a positive spherical aberrationfor the near focus. The combination of the diffractive structure 120′and the base curvature 130′ may, therefore, provide sphericalaberrations having opposite signs in the near and far focus. Theintensity profiles for the lens 110′ may thus be analogous to those 140′and/or 142′ of the lens 110.

The lens 110′ may share the benefits of the lens 110. In particular, thelens 110′ may have improved performance while maintaining the benefitsof a multifocal lens. Because the lens 110′ is a multifocal lens, theophthalmic device 100 may be used to treat conditions such aspresbyopia. Because the diffractive structure 120′ and the basecurvature 130′ are employed, the visual disturbances for the lens 110′may be reduced. More specifically, visual disturbances such a ghostimages may be decreased in intensity and depth of field improved. As aresult, performance of the ophthalmic lens 110′ may be enhanced.

FIG. 5 depicts a side view of another exemplary embodiment of a lens110″ of an ophthalmic device. The lens 110″ is analogous to the lens(es)110 and/or 110′. Consequently, the lens 110″ may be used in anophthalmic devices such as the device 100. Further, analogous componentshave similar labels. The lens 110″ includes an anterior surface 112″, aposterior surface 114″, an optic axis 116, base curvature 130″ anddiffractive structure 120″ having echelettes 122″ that are analogous tothe anterior surface 112/112′, posterior surface 114/114′, optic axis116, base curvature 130/130′ and diffractive structure 120/120′ havingechelettes 122/122′, respectively, of the lens(es) 110/110′.

In the lens 110″, the diffractive structure 120″ and base curvature 130″both reside on the anterior surface 112″. This is possible because theprofile of the anterior surface 112″ is the sum of the profiles of thediffractive structure 120″ and the base curvature 130″. The diffractivestructure 120″ and base curvature 130″ introduce spherical aberrationshaving opposite signs and, in some embodiments, different magnitudes.Thus, the base curvature 130″ may introduce a negative sphericalaberration for the at least the far focus. The diffractive structure120″ introduces a positive spherical aberration for the near focus. Thecombination of the diffractive structure 120″ and the base curvature130″ may provide spherical aberrations having opposite signs in the nearand far focus. The intensity profiles for the lens 110″ may thus beanalogous to those 140′ and/or 142′ of the lens 110.

The lens 110″ may share the benefits of the lens(es) 110 and/or 110′.The lens 110″ may have improved performance while maintaining thebenefits of a multifocal lens. Because the lens 110″ is a multifocallens, the ophthalmic device 100 may be used to treat conditions such aspresbyopia. Because the diffractive structure 120″ and the basecurvature 130″ are employed, the visual disturbances for the lens 110″may be reduced. More specifically, visual disturbances such a ghostimages may be decreased in intensity and depth of field improved. As aresult, performance of the ophthalmic lens 110″ may be enhanced.

FIG. 6 depicts a side view of another exemplary embodiment of a lens110′″ of an ophthalmic device. The lens 110′″ is analogous to thelens(es) 110, 110′ and/or 110″. Consequently, the lens 110′″ may be usedin an ophthalmic devices such as the device 100. Further, analogouscomponents have similar labels. The lens 110′″ includes an anteriorsurface 112′″, a posterior surface 114′″, an optic axis 116, basecurvature 130′″ and diffractive structure 120′″ having echelettes 122′″that are analogous to the anterior surface 112/112′/112″, posteriorsurface 114/114′/114″, optic axis 116, base curvature 130/130′/130″ anddiffractive structure 120/120′/120″ having echelettes 122/122′/122″,respectively, of the lens(es) 110/110′/110″.

In the lens 110′″, the diffractive structure 120′″ and base curvature130′″ both reside on the posterior surface 114′″. The lens 110′″ is thusmost analogous to the lens 110″. The profile of the posterior surface114′″ is the sum of the profiles of the diffractive structure 120′″ andthe base curvature 130′″. The diffractive structure 120′″ and basecurvature 130′″ introduce spherical aberrations having opposite signsand, in some embodiments, different magnitudes. Thus, the base curvature130′″ may introduce a negative spherical aberration for the at least thefar focus. The diffractive structure 120′″ introduces a positivespherical aberration for the near focus. The combination of thediffractive structure 120′″ and the base curvature 130′″ may, therefore,provide spherical aberrations having opposite signs in the near and farfocus. The intensity profiles for the lens 110′″ may thus be analogousto those 140′ and/or 142′ of the lens 110.

The lens 110′″ may share the benefits of the lens(es) 110, 110′ and/or110″. The lens 110′″ may have improved performance while maintaining thebenefits of a multifocal lens. Because the lens 110′″ is a multifocallens, the ophthalmic device 100 may be used to treat conditions such aspresbyopia. Because the diffractive structure 120′″ and the basecurvature 130′″ are employed, the visual disturbances for the lens 110′″may be reduced. More specifically, visual disturbances such a ghostimages may be decreased in intensity and depth of field improved. As aresult, performance of the ophthalmic lens 110′″ may be enhanced.

FIG. 7 depicts a side view of another exemplary embodiment of a lens 150of an ophthalmic device. The lens 150 is analogous to the lens(es) 110,110′, 110″ and/or 110″. Consequently, the lens 150 may be used in anophthalmic devices such as the device 100. Further, analogous componentshave similar labels. The lens 150 includes an anterior surface 152, aposterior surface 154, an optic axis 156, base curvature 170 anddiffractive structure 160 having echelettes 162 that are analogous tothe anterior surface 112/112′/112′/112″, posterior surface114/114′/114″/114′″, optic axis 116, base curvature 130/1307130″M 30′″and diffractive structure 120/120′/120″/120′″ having echelettes122/122′/122″/122′″, respectively, of the lens(es) 110/110′/110″/110′″.

In the lens 150, the diffractive structure 160 resides on the anteriorsurface 152, while the base curvature 170 resides on the posteriorsurface 154. Thus, the lens 150 may be considered most analogous to thelens 110. In addition, the lens 150 is a trifocal lens. In otherembodiments, the lens 150 may have another number of focuses. Forexample, the lens 150 might be a quadrafocal lens.

The diffractive structure 160 and base curvature 170 introduce sphericalaberrations having opposite signs and, in some embodiments, differentmagnitudes. Thus, the base curvature 170 may introduce a negativespherical aberration for the at least the far focus. The base curvature170 may also provide a negative spherical aberration for the near and/orintermediate focuses. The diffractive structure 160 may introduce twospherical aberrations for the intermediate focus and the near focus. Forexample, the diffractive structure 10 may have a first positivespherical aberration for the near focus and a second positive sphericalaberration for the intermediate focus. In some cases, the secondspherical aberration has a smaller magnitude than the first sphericalaberration. The near and far intensity profiles for the lens 150 maythus be analogous to those 140′ and/or 142′ of the lens 110. Thus, atleast the near and far focus have spherical aberrations that areopposite in sign. The intensity profile for the intermediate focus maybe analogous.

The lens 150 may share the benefits of the lens(es) 110, 110′, 110″and/or 110′″. The lens 150 may have improved performance whilemaintaining the benefits of a multifocal lens. Because the lens 150 is amultifocal lens, the ophthalmic device 100 may be used to treatconditions such as presbyopia. Because the diffractive structure 160 andthe base curvature 170 are employed, the visual disturbances for thelens 150 may be reduced. More specifically, visual disturbances such aghost images may be decreased in intensity and depth of field improved.As a result, performance of the ophthalmic lens 150 may be enhanced

FIG. 8 is an exemplary embodiment of a method 200 for treating anophthalmic condition in a patient. For simplicity, some steps may beomitted, interleaved, and/or combined. The method 200 is also describedin the context of using the ophthalmic device 100 and ophthalmic lens110. However, the method 200 may be used with one or more of ophthalmiclenses 110, 110′, 110″, 110′″ and/or an analogous ophthalmic device.

An ophthalmic device 100 for implantation in an eye of the patient isselected, via step 202. The ophthalmic device 100 includes an ophthalmiclens 110 having a diffractive structure 120 and base curvature 130 thatintroduce spherical aberrations having opposite sign and, optionally,magnitude. Thus, the ophthalmic device 100 including the ophthalmic lens110, 110′, 110″, or 110′″ may be selected in step 202.

The ophthalmic device 100 is implanted in the patient's eye, via step204. Step 204 may include replacing the patient's own lens with theophthalmic device 100 or augmenting the patient's lens with theophthalmic device. Treatment of the patient may then be completed. Insome embodiments implantation in the patient's other eye of anotheranalogous ophthalmic device may be carried out.

Using the method 200, the ophthalmic lens(s) 110, 110′, 1110″, 110′″and/or ophthalmic lens may be used. Thus, the benefits of one or more ofthe ophthalmic lenses 110, 110′, 110″, and/or 110′″ may be achieved.

A method and system for providing an ophthalmic device have beendescribed. The method and systems have been described in accordance withthe exemplary embodiments shown, and one of ordinary skill in the artwill readily recognize that there could be variations to theembodiments, and any variations would be within the spirit and scope ofthe method and system. Accordingly, many modifications may be made byone of ordinary skill in the art without departing from the spirit andscope of the appended claims.

We claim:
 1. An ophthalmic lens, comprising: an optic having a basecurvature adapted to provide a base power defining a first focus and afirst spherical aberration corresponding to the first focus; and adiffractive structure adapted to provide a second focus and a secondspherical aberration corresponding to the second focus, the secondspherical aberration having an opposite sign relative to the firstspherical aberration; wherein the first spherical aberration has a firstmagnitude, and the second spherical aberration has a second magnitudegreater than the first magnitude.
 2. The ophthalmic lens of claim 1,wherein the diffractive structure includes a first diffractive order forthe first focus and a second diffractive order for the second focus. 3.The ophthalmic lens of claim 2, wherein the first diffractive order isthe 0^(th) order and the second diffractive order is the 1^(st) order.4. The ophthalmic lens of claim 1, wherein the first sphericalaberration is a negative spherical aberration and the second sphericalaberration is a positive spherical aberration.
 5. The ophthalmic lens ofclaim 1, wherein the first focus corresponds to distance vision, and thesecond focus corresponds to near vision.
 6. The ophthalmic lens of claim1, wherein the diffractive structure is adapted to split light betweenthe first focus corresponding to a first focal length and the secondfocus corresponding to a second focal length.
 7. The ophthalmic lens ofclaim 6, wherein the diffractive structure is adapted to split lightbetween the first focus corresponding to the first focal length, thesecond focus corresponding to the second focal length, and a third focuscorresponding to an intermediate focal length that is between the firstfocal length and the second focal length.
 8. The ophthalmic lens ofclaim 7, wherein: the diffractive structure provides a third sphericalaberration corresponding to the third focus; and a magnitude of thethird spherical aberration is less than a magnitude of the secondspherical aberration.
 9. The ophthalmic lens of claim 1, wherein theophthalmic lens is one of an intraocular lens and a contact lens.
 10. Amultifocal ophthalmic lens, comprising: an optic having a base curvatureadapted to provide a base power defining a far focus corresponding to afirst focal length and a negative spherical aberration corresponding tothe far focus and having a first magnitude; and a diffractive structureadapted to: distribute light between the far focus corresponding to thefirst focal length and a near focus corresponding to a second focallength, and provide a positive spherical aberration corresponding to thenear focus, the positive spherical aberration having a second magnitudegreater than the first magnitude of the negative spherical aberration.11. The multifocal ophthalmic lens of claim 10, wherein the diffractivestructure is further adapted to distribute light to an intermediatefocus between the far focus and the near focus.
 12. The multifocalophthalmic lens of claim 11, wherein: the diffractive structure providesa third spherical aberration corresponding to the intermediate focus;the sign of the third spherical aberration is positive; and the thirdspherical aberration has a third magnitude less than the secondmagnitude.
 13. The multifocal ophthalmic lens of claim 10, wherein themultifocal ophthalmic lens is one of an intraocular lens and a contactlens.